Some of pressure sensors include a joint, a sensor module attached to the joint, and a diaphragm provided on the sensor module and displaceable in accordance with a pressure of a fluid to be measured.
An example of the above pressure sensors include: a cylindrical member having a flange and a distal end closed by a diaphragm; and an attachment base having a counterbore for receiving the cylindrical member (Patent Literature 1: Japanese Patent Publication No. 4127532).
According to Patent Literature 1, the cylindrical member is inserted from an insertion hole of the attachment base and the flange is fitted into the counterbore. In this state, a pressurizing force in an axial direction is applied to the cylindrical member so that a coarse face at a distal end face of the flange bites into a bottom face of the attachment base. Further, a punch is lowered concentrically with the insertion hole of the attachment base for the cylindrical member. According to the above process, the attachment base and the cylindrical member are bonded by a plastic deformation bonding (so-called “metal flow”), so that an assembly process of the attachment base and the cylindrical member can be facilitated and air-tightness can be enhanced.
According to the typical example disclosed in Patent Literature 1, the cylindrical member is provided by a single member. When a pressure is applied to the cylindrical member toward the attachment base using a punch or the like in order to attach the attachment base and the cylindrical member to each other, the pressurizing force may be transmitted to the diaphragm to cause a strain on the diaphragm.
Since a detector is usually provided on the diaphragm, the detection accuracy of the detector is influenced by the assembly process.